1. Field of the Invention
This invention is related generally to the manufacture and direct use of waterbearing gels as hot melt glues, and specifically to a water soluble, biodegradable, repulpable, waterbearing gelatinous product based on natural organic animal, mineral and/or vegetable thermoreversible waterbearing gels which are capable of being heated and applied with automatic hot melt glue application equipment, such as automatic piston and gear pump hydraulic glue application equipment for packaging sealing purposes, such as for bag sealing, tray making and corrugated carton closure. This invention also is directed generally to products made from a further modified product of the waterbearing gelatinous product of this invention, and specifically to fishing lures in the form of artificial baits, such as worms, which are extruded, cast, or injection molded from the hot melt glue.
2. Prior Art
Waterbearing gels, or colloids, as a general class are known by those skilled in the art. Such waterbearing gels include a wide variety of thermally reversible gels, typically in the form of semi-solid masses. These semi-solid masses generally are supersaturated solid materials in which the water molecule is chemically bound to the solid material.
Likewise, hot melt glues and application equipment for applying hot melt glues also are known to those skilled in the art. Current hot melt glues are 100% solid polymeric materials which are reduced to molten thermoplastic materials by heating. A typical hot melt glue is a solid, thermoplastic hydrocarbon material which quickly melts upon heating, and then sets to a bond on cooling, unlike other types of glues which set upon evaporation of a solvent. The materials from which current hot melt glues are made have a high degree of tack, or stickiness, when molten, and are solid upon cooling. Examples of raw materials for hot melt glues include polyethylene, polyvinyl acetate, hydrocarbon resins, asphalts, bitumens, and waxes.
Some examples of current polymeric hot-melt adhesives include the adhesive disclosed in U.S. Pat. No. 4,656,242 describing a polyesteramide composition comprising the polymerization product of a polymeric fatty acid and a dicarboxylic acid, with a substantially equivalent amount of an organic diamine and a diol. The main use for this type of hot-melt adhesive is for metals and plastics, and use in connection with cardboard or other paper products is not disclosed. Another similar hot-melt adhesive is disclosed in U.S. Pat. No. 4,569,985, which discloses an adhesive comprising a polymeric fatty acid, a dicarboxylic acid, an organic diamine and an alkanolamine. This type of hot-melt adhesive is suggested for use in connection with PVC films and no mention of cardboard or other paper products is made. Another general polymeric hot-melt adhesive is disclosed in U.S. Pat. No. 4,602,058, which discloses a hot-melt adhesive comprising polyamides, ethylene polymer containing carboxylic acid groups, organic carboxylic acid compounds and a free radical scavenger or antioxidant. The addition of the organic carboxylic acid improves the thermal stability of the blend. As these three hot-melt adhesives are polymer based, they do not possess the environmentally friendly characteristics which are desirable.
Current hot melt adhesives are applied at temperatures of from between 300.degree. F. and 450.degree. F. All of these materials tend to char in the hot melt glue application system, which eventually causes clogging of the system's dispensing heads. Additionally, due to the high temperatures of application, these products cause severe burns if they come in contact with human skin. These prior art products also are flammable.
Other glues, particularly glues used in the furniture and bookbinding industries, are based upon animal glue manufactured from animal bone and hide resins, fish, blood, and casein. However, in order to use these animal based gelatin glues, the glue has to be melted from a supply gel or cooked from a dry powder and diluted with water prior to application. This dilution typically increases the water content of the glue from 75% to 85%. The additional water changes the nature of the adhesive from a gel to a liquid, thus allowing the application of a very thin film from which water could evaporate, thus causing a bond. The addition of so much water causes problems such as board warpage and location control in many applications, causing manufacturers to use other types of adhesives, such as those with solvent and hydrocarbon bases. Other water-based glues are available, and, like solvent-based materials, are dependent on the evaporation of the solvent to form a strong bond. The evaporation process makes such glues slow to set relative to the hot melt glues, which need only to cool to form a bond. However, as a class, such glues cannot be recycled and are not biodegradable.
Current commercial hot melt glue application equipment is produced by many different manufacturers, including ITW Dynatec and Nordson. The typical hot melt glue application system consists of a heated melting pot, a hydraulic pumping means of either the gear or piston type, a heated feed line, and a heated dispensing head of various designs to apply the liquefied glue material to the substrate being bonded. In general, the hot melt glue application system is in the form of a glue gun. Such guns are well-known and commercially available and in widespread use. Because of the high operating temperatures of the glue guns, they can cause burns to operators and servicing persons.
Several representative hot-melt glue application devices include the hot-melt adhesive gun disclosed in U.S. Pat. No. 4,199,082; the hot-melt cartridge adhesive gun disclosed in U.S. Pat. No. 4,034,484; the hot-melt adhesive applicator gun disclosed in U.S. Pat. No. 4,601,597; and the hot-melt adhesive applicator gun disclosed in U.S. Pat. No. 4,463,877. Each of these guns heats the hot-melt adhesive so as to melt the adhesive in preparation for applying the adhesive to the substrate. Obviously, the hotter the temperature needed to heat the adhesive, the hotter the guns themselves will become. It can be seen that with a lower melting temperature adhesive, lower temperature guns can be used, thus lessening the danger to the operator.
Thus, it can be seen that there is a need for a water soluble, biodegradable, repulpable, glue manufactured from a renewable resource which will have the processing speeds of hot melt glues and the environmental advantages of water based glues. The hot melt glue disclosed and claimed herein is low-cost and environmentally safe and, unlike prior natural adhesives, has a superior handling and application quality and a broad range of industrial applicability.